1. Field of the Invention
The present invention relates to power saving control in an image forming system having an image forming apparatus and a post-processing apparatus for carrying out post-processing on a sheet outputted from the image forming apparatus.
2. Description of the Related Art
As described in Japanese Patent Application Laid-open No. H11-139677, there is a system which is provided with an image forming apparatus of an electrophotographic printing method and a post-processing apparatus for carrying out a stapling process, adhesive bookbinding, etc., and which shifts the post-processing apparatus to a power saving state in operative association with the power saving of the image forming apparatus to thereby realize power saving.
Also, in recent years, a large-scale image forming system in which a plurality of post-processing apparatuses are connected in tandem to an image forming apparatus to thereby realize a wide variety of functions including a bookbinding function has been proposed for a print on-demand market. FIG. 10 of the accompanying drawings schematically shows the construction of the conventional large-scale image forming system. This image forming system is of a construction in which an image forming apparatus 1201, a large-capacity paper deck 1202, a sorting apparatus 1203, a stacker 1204 and a finisher 1205 are connected together in series. In this image forming system, the power saving of the entire image forming system is achieved by bring about a power saving state in which a post-processing apparatus is not operated in operative association with the power saving of the image forming apparatus when the image forming apparatus has been brought into an unused state.
In the above-described conventional image forming system, however, the post-processing apparatus could not singly be shifted to the power saving state, irrespective of the operative state of the image forming system. Therefore, in a post-processing apparatus such as, for example, an adhesive bookbinding apparatus provided with a heating heater for melting paste and high in electric power consumption, wasteful electric power has been consumed by the heating heater being normally rendered ON even when only an operation of delivering a sheet to a downstream post-processing apparatus is performed.
Thus, heretofore, an upstream post-processing apparatus could not be shifted to a power saving state in which only the delivery of the sheet to the downstream post-processing apparatus is possible and therefore, electric power has been wastefully consumed.